Scatterometers provide a simple, nondestructive monitoring and evaluation technique to determine the surface microstructure of a sample. Generally, a scatterometer facilitates measurement of the directional energy distribution of radiation reflected from a sample surface. For example, if the sample surface is perfectly mat then the reflected radiation is diffuse, i.e., equal in all directions, whereas if the sample surface is not perfectly mat then the reflected radiation has a specular component, i.e., more concentrated in certain directions. This technique is useful in many areas of technology where observation of surface characteristics is evaluated.
Substrate materials having visually opaque coatings are often subject to physical/chemical changes. For example, substrate material may be susceptible to corrosion or heat damage which alter the substrate surface characteristic. The substrate coating, however, prevents a simple visual inspection of the nature of the underlying substrate surface.
It is therefore evident that there exists a need in the art for a method to evaluate substrate surface conditions of coated substrates where such method is nondestructive and is relatively simple to perform.